Integrated circuits include circuit components that are interconnected via conductive paths. These paths may be used to route data signals, control signals, and other electrical signals from one circuit component to another. Signals that are conveyed over these conductive paths may experience respective amounts of path delay (i.e., the amount of time it takes for an electrical signal to propagate through a wired path).
The path delay for at least some of the conductive paths on an integrated circuit may be critical. For example, consider a scenario in which a data signal is conveyed over a first path and a data strobe signal that is associated with the data signal is conveyed over a second path. The path delay of the first path and the path delay of the second path should be configured such that the data signal and its associated data strobe signal are properly synchronized with respect to one another (i.e. so that the rising clock edge of the data strobe signal is properly aligned with respect to the rising clock edge of the data signal). Mismatch (or skew) in path delay between the first and second paths may result in degraded timing margins.
In an effort to provide path delays for optimizing performance, calibration techniques that are performed during device startup have been developed. Conventional startup calibration techniques involve adjusting a delay chain in a path under calibration so that the path under calibration provides the desired path delay. Performing calibration operations using this approach may be effective in calibrating static sources of variation such as process variations but may fail to take into account dynamic sources of variation (e.g., operating temperature and power supply voltage levels can drift over time).
To compensate for dynamic sources of variation, runtime tracking circuitry may be used to monitor operating conditions that vary during normal operation of the integrated circuit. Runtime tracking circuitry may help reclaim additional timing margin by tracking low frequency variations (i.e., variations that vary sufficiently slow over time) and by adjusting the delay chains accordingly. Conventional runtime tracking circuitry monitors the actual path delays and may sometimes require interrupting system operation, which may be unacceptable to a user of the integrated circuit.